China Mobile: 400,000 Unlocked iPhones On Our Network (AAPL)

An eye-opening stat we hadn't seen until today: China Mobile, the biggest wireless carrier in China, said there were 400,000 unlocked iPhones operating on its network at the end of 2007.

If true, that represents more than 10% of the 3.7 million iPhones Apple (AAPL) sold last year. Market research firm In-Stat, which included the stat in an email newsletter today, said that total was four times what they had previously estimated. That helps explain where many of the "missing" iPhones have wound up.

This is mixed news for Apple: The company makes a profit on every iPhone it sells, whether it's activated via one of its wireless carriers or not.

But a big part of Steve Jobs' iPhone income comes from carriers, which pay Apple a percentage of the service revenue they get from iPhone owners. Some analysts estimate that AT&T, Apple's exclusive U.S. carrier partner, pays Apple $15 per month, per iPhone subscriber -- $360 over the length of a 2-year contract -- which is pure profit.